Leakage Loss Flow Control

ABSTRACT

A rotating piston machine includes a driving rotor and a driven rotor, the axes of rotation of the rotors enclosing a particular axial angle. The rotors include gear teeth which mesh with one another. One of the rotors is adjustable axially in the housing and is acted upon by an adjusting force which counteracts the force brought about by the working pressure and a short circuiting gap between the gear teeth of the rotors by virtue of the appropriate displacement of the rotor.

The invention starts out from a rotating piston machine, which can operate as a pump, a compressor or an engine, of the type described in the main claim. In the case of a known rotating piston machine of the generic type (German patent 42 41 320, European patent 1,005,604), a high leakproofness between the working chambers is aimed for also by means of the configuration of the teeth, in order to keep the leakage as small as possible from one working chamber to the adjacent working chamber over the flanks with line contact between driving a driving rotor and a driven rotor and vice versa. In this connection, the crests of the tooth of one rotor proceed linearly at the flanks of the other rotor, the course of the working surface of which is cycloidal.

The output, required from such a rotating piston machine, varies depending on the use, to which it is put. For this purpose, different control and regulating methods are known. The simplest method is to combine the pressure and suction sides of the machine. However, with regard to the high energy taken up by the machine, this makes hardly any difference. In many cases, especially when used as a lubricating pump in the motor vehicle sector, but also when used as a presupply pump for a diesel fuel injection systems, every effort is made to keep the energy, taken up by the machine, as low as possible and to adapt it to the actual power output (see German Offenlegungsschrift 100 25 723).

In comparison to the above, the inventive rotating piston machine with the characterizing distinguishing features of the main claim has the advantage that the energy, taken up by the rotating piston machine, corresponds directly to the power output of the same. A leakage loss of such a machine, which can never be avoided completely, has become a quantity control or loss quantity control, which is brought about by a selective change in the gap width. A further advantage consists therein that foaming, which may arise, for example, when controlling the return channel, is largely prevented, for example, when fuel or oil is pumped.

Admittedly, it is known that, by connecting the suction side with the pressure side directly (DE 100 25 723), a corresponding decrease in energy uptake can be achieved in fuel pumps. However, such systems do not involve working chambers located on the front faces of the rotors and, instead, are concerned with gear pumps with radially disposed cogs or annular gears with a completely different mode of operation from the very start (displacement in the axial direction), so that such variously know solutions cannot be used for the invention. Accordingly, for an oil pump, which also works with a gear wheel and an annular gear, it is known (U.S. Pat. No. 5,085,187) that the pump working chambers may be closed off laterally by a lid, which is shifted when the pumping pressure is sufficiently high, so that a connection is established between the suction space and the pressure space of the oil pump.

For adapting the energy uptake to the actual power output of rotating piston machines with gearing at the front (U.S. Pat. No. 2,049,775), it is known that the driven rotor may be swiveled within a spherical bearing, in order to change the axial angle between the axes of rotation by these means, which may lead correspondingly to a change in the amount pumped up to a zero amount pumped. It is a disadvantage of such a construction that the costs of construction are considerably higher and the output capability is more limited. Moreover, above all, the sealing of the working chambers from the adjusting device is a disadvantage.

According to an advantageous development of the invention, at least the axially displaceable rotor is guided axially and radially in a corresponding, cylindrical control space of the machine housing. The displaceable rotor, moreover, is disposed equiaxially with the cylindrical control space.

According to an embodiment of the invention, which is advantageous in this respect, the adjusting force is arbitrarily controllable and works with hydraulic, gaseous and/or electrical means. It is of decisive importance that forces on the back of the rotor counteract the pressures in the working chambers, in order to control the desired axial displacement of the rotor and, with that, the leakage between the working chambers.

According to an additional development of the invention, the chamber, which is bounded by the back of the rotor, is closed off pressure tight in order to produce an adjusting force by means of a liquid or gaseous medium.

According to a development of the invention, which is advantageous in this regard, the medium pumped generates the adjusting force. By these means, the delivery pressure of the machine can be used directly to regulate the adjusting force. Correspondingly, according to a development of the invention, there is a connection between the working chambers and the control space for the medium delivered.

According to an additional advantageous development of the invention, one of the rotors (shaft rotor) is constructed spherically on the side averted from the working chamber and supported in a correspondingly spherical recess in the housing. The radial support of the rotor can cut into this sphere in order to fix the axial axis of rotation of the rotor.

According to an additional, advantageous development of the invention, there is, at the rotors in the middle region of the front side centrally a spherical surface at a rotor. This spherical surface is supported on a corresponding spherical recess at the other rotor and forms the boundary of the working chambers radially to the inside. By the axial displacement of the one rotor, an additional connection for the leakage between the working chambers is produced over this region.

Further advantages and advantageous developments of the invention may be inferred from the following description, the drawing and the claims.

An example of the object of the invention is shown in the drawing and explained in greater detail in the following. The embodiment is a fuel delivery pump, which is shown in longitudinal section.

An inlay 2 is disposed in a housing 1 so that it cannot twist. A counter rotor 3, which interacts with a shaft rotor 4, which is driven from outside the pump, is disposed rotatably and radially guided and axially displaceably in the housing 1. On mutually facing front sides, the shaft rotor 4 and the counter rotor 3 have meshing gearings, through which working chambers are separated from one another in a known manner and over which the counter rotor 3 is driven by the shaft rotor 4. One of the two front gearings has a cycloidal cross section, in order to form by these means a linear connection between the gear crests of the other part and this cycloidal surface. The working chambers, the details of which are not shown here and the capacity of which changes continuously during the operation because of the changing angle between the axes of rotation of the rotors 3 and 4, are connected corresponding to their pumping task with a suction channel (suction kidney) and a pressure channel (pressure kidney).

The counter rotor 3 is disposed rotatably in a plain bearing bush 5. Between the plain bearing bush 5 and the counter rotor 3, a plain bearing shaft 6 is disposed, which is supported radially and axially in the plain bearing bush 5 and, together with the counter rotor 3, can be shifted axially within the plain bearing bush 5.

The shaft rotor 4 is also supported radially and axially in a plain bearing 7. The hat-shaped end of a drive shaft 8 protrudes between the shaft rotor 4 and the plain bearing bush 7 and the shaft rotor 4 dips with a corresponding cylindrical section into this hat-shaped formation. Between the bottom of the hat-shaped section of the drive shaft 8 and the dipping section of the shaft rotor 4, a spring 10 is disposed, which, on the one hand, carries along the shaft rotor 4 as the shaft 8 rotates and, on the other, puts the shaft rotor 4 under a load in the direction of the counter rotor 3.

On the side averted from the shaft 8, the housing 1 is closed off by lids 11 and 12. The lid 11 on the inside is supported on, the one hand, at the plain bearing bush 5 and, on the other, at the lid 12 on the outside, which functions as the actual closing part of the housing 1 of the pump and is secured in its axial position towards the outside by a retaining ring 9.

Pursuant to the invention, the counter rotor 3 is displaceable axially in the direction of its axis of rotation. Pursuant to the invention, this displacement can be accomplished with appropriate means, the pressure, developing in the working chambers, forming a corresponding adjusting force, which affects the counter rotor 3. This adjusting force acts counter to a restoring force, which is formed in the example shown, by liquid, and acts on the section of the counter rotor, which dips into the plain bearing bush 5 and is averted from the working chambers. To control this counter force, there is a connection (not shown) between these chambers, the forces having to be matched to one another, especially because of the surfaces acted upon.

An insert 13 is disposed in the inlay 2 in the area of the shaft 8 so as to form a seal. It holds the plain bearing 7 axially and, furthermore, accommodates a plain bearing seal 17, in which the shaft 8 is disposed, so that it can rotate. Moreover, the shaft 8 is supported by a ball bearing 18 in this inlay insert 13. O rings 16 provide the necessary seal between this inlay insert 13 and the inlay 2, as well as between the inlay 2 and the housing 1.

All the distinguishing features, shown in the specification, in the claims that follow and in the drawing, may be essential to the invention individually as well as in any combination with one another. 

1.-8. (canceled)
 9. A rotary piston machine operable as at least one of a pump, a compressor and an engine, comprising: a driving rotor and driven rotor including at least two interacting, movable rotary pistons, respective axes of rotation of said driving rotor and said driven rotor being arranged at a particular axial angle to one another, mutually meshing gears being disposed on front sides of the rotors facing one another; a machine housing in which the driving rotor and the driven rotor are supported radially and axially, axial front sides of the machine housing forming a boundary of working chambers, mounting of at least one of said driving rotor and said driven rotor in the machine housing being axially adjustable in the direction of the axis of rotation of the driven rotor, an axial adjusting force which counteracts another force brought about by the working pressure in the working chamber engaging the driven rotor, a magnitude of said adjusting force being variable in order to counteract a short circuiting gap between said working chambers, which are separated from one another by the gears of the rotors, by axially displacing the driven rotor in the direction of the axis of rotation; and a suction channel and a pressure channel provided in the machine housing connectable with the working chambers intermittently when said driving rotor and said driven rotor are running.
 10. A rotary piston machine according to claim 9, wherein at least the axially displaceable driven rotor is guided axially and radially in a correspondingly cylindrical control space of the machine housing.
 11. A rotary piston machine according to claim 9, wherein the adjusting force is arbitrarily controllable and operates on at least one of a hydraulic, a gaseous and an electric basis.
 12. A rotary piston machine according to claim 10, wherein the adjusting force is arbitrarily controllable and operates on at least one of a hydraulic, a gaseous and an electric basis.
 13. A rotary piston machine according to claim 10, wherein the cylindrical control space can be closed off in a substantially pressure-tight manner.
 14. A rotary piston machine according to claim 11, wherein the cylindrical control space can be closed off in a substantially pressure-tight manner.
 15. A rotary piston machine according to claim 12, wherein the cylindrical control space can be closed off in a substantially pressure-tight manner.
 16. A rotary piston machine according to claim 9, wherein a medium is to be pumped by said rotary piston machine, said medium generating the adjusting force.
 17. A rotary piston machine according to claim 16, wherein a connection is provided between the working chambers and the control space for the medium that is to be pumped.
 18. A rotary piston machine according to claim 9, wherein the driving rotor is constructed spherically on a side thereof averted from the working chambers and is supported in a correspondingly spherical recess in the machine housing.
 19. A rotary piston machine according to claim 6, wherein a spherical surface is formed in a middle region of a front side of one of the rotors, said spherical surface being supported at a corresponding spherical recess formed in a remaining one of the rotors and forming the boundary of the working chambers radially to the center.
 20. A rotary piston machine, comprising: a driving rotor and driven rotor including each including a respective movably interacting rotary piston, respective axes of rotation of said driving rotor and said driven rotor being arranged at a particular axial angle to one another, mutually meshing gears including teeth being disposed on front sides of the rotors facing one another; a machine housing in which the driving rotor and the driven rotor are supported radially and axially, axial front sides of the machine housing forming a boundary of working chambers, mounting of at least one of said driving rotor and said driven rotor in the machine housing being axially adjustable in the direction of the axis of rotation of the driven rotor, an axial adjusting force being provided which counteracts another force brought about by the working pressure in the working chamber by engaging the driven rotor, a magnitude of said adjusting force being variable in order to regulate a short circuiting gap between said working chambers, which are separated from one another by the teeth of the rotors, by axial displacement of the driven rotor in the direction of the axis of rotation; and a suction channel and a pressure channel being disposed in the machine housing and connectable with the working chambers intermittently when said driving rotor and said driven rotor are running.
 21. A rotary piston machine, comprising: a driving rotor and driven rotor, respective axes of rotation of said driving rotor and said driven rotor being arranged at a particular axial angle to one another, gears including mutually meshing teeth being carried on front sides of the rotors facing one another; a machine housing in which the driving rotor and the driven rotor are supported radially and axially, axial front sides of the machine housing forming a boundary of working chambers, mounting of at least one of said driving rotor and said driven rotor in the machine housing being axially adjustable along a direction of the axis of rotation of the driven rotor, a suitable axial adjusting force being provided which counteracts another force, brought about by the working pressure in the working chamber, by engaging the driven rotor in order to diminish presence of a short circuiting gap between said working chambers, which are separated from one another by the teeth of the rotors, by axial displacement of the driven rotor along the direction of the axis of rotation; and a suction channel and a pressure channel being disposed in the machine housing and connectable with the working chambers intermittently when said driving rotor and said driven rotor are running.
 22. A rotary piston machine according to claim 21, wherein a magnitude of said adjusting force is variable. 